Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session H31: Electronic Structure of Quantum Systems IFocus

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Sponsoring Units: DCP Chair: Deryou Kao, NASA Goddard Space Flight Center Room: BCEC 203 
Tuesday, March 5, 2019 2:30PM  3:06PM 
H31.00001: TBD Invited Speaker: Coen de Graf N/A 
Tuesday, March 5, 2019 3:06PM  3:42PM 
H31.00002: Improving the prediction of magnetic interactions from DFT methods: Noncollinear magnetization and selfinteraction Invited Speaker: Juan Peralta Electronic structure methods are routinely used to predict magnetic properties of diverse materials, including molecular nanomagnets, clusters, and crystals. Density functional theory (DFT) has been one of the workhorses of modern electronic structure methods, and as such, it has been used extensively for the prediction of magnetic properties. In this talk I will summarize our efforts to improve the prediction of magnetic exchange couplings J from DFT methods in two fronts. First, I will show a proposed method to extract J based on differential rotations of the local atomic magnetization. This method avoids the explicit evaluation of energy differences, which can become impractical for large complexes and clusters. Our approach is based on the evaluation of the transversal magnetic torque between magnetic centers using constraints of the local magnetization direction via Lagrange multipliers and involves noncollinear spin DFT.[1] This, combined with a local partitioning of 〈S^{2}〉, [2] makes possible the evaluation of J couplings entirely from first principles without adhoc nominal spin values. Second, I will show how selfinteraction error (SIE) impacts the prediction of J couplings using an efficient implementation for SIE removal based on FermiLöwdin orbitals (FLOSIC).[3] Using this method, removing SIE from the simple local spin density approximation improves calculated J couplings,[4] in line with previous observations for small model systems. 
Tuesday, March 5, 2019 3:42PM  3:54PM 
H31.00003: Efficient Implementation of RTTDDFT on Siesta 4.0 Fernando Vila, Marilena Tzavala, John Rehr Realtime timedependent DFT (RTTDDFT) provides a versatile method for computing electronic response in both linear and nonlinear regimes. Here we introduce RTSiesta4, an efficient implementation of RTTDDFT which combines the LCAO approach for electronic structure in Siesta 4.0 with an efficient CrankNicolson timeevolution operator to propagate KohnSham states in the presence of an external electric field. This development extends our previous implementation with Siesta 2.0.^{1} RTSiesta4 uses a predictorcorrector scheme to ensure timereversibility, thus enabling long time steps. Its capabilities include full spectrum linear optical response, single frequency NLO response, and response to shaped pulses. Benchmarks for typical systems are presented showing how the faster evaluation of the TD Hamiltonian in Siesta 4.0 improves the performance of our realtime implementation. Finally, we discuss the need to extend scalability into the peta and exascales. 
Tuesday, March 5, 2019 3:54PM  4:06PM 
H31.00004: Performance of Generalized Gradient Approximations with Nearly Correct Asymptotic Potentials on Molecular and SolidState Properties Alberto Vela, Angel AlbaveraMata, Karla Botello Mancilla, Javier CarmonaEspindola, Sam B Trickey, Jose L Gazquez The recently developed nearly correct asymptotic potential (NCAP) and its predecessor (CAP) are generalized gradient approximations (GGAs) for exchange and correlation designed to capture the asymptotic behavior of the exchange potential [1,2]. Compared to more common GGAs, they improve the description of frequencydependent response properties in molecules, yet provide good accuracy of thermodynamic and kinetic properties. NCAP incorporates a potential shift accounting for the derivative discontinuity of the potential and has an overall performance, for molecules, competitive with current metaGGAs. In this work, we present and discuss the performance of these GGAs on extensive tests involving lattice constants, bulk moduli, and cohesive energies for a set of solids and compare that performance with molecular results. 
Tuesday, March 5, 2019 4:06PM  4:18PM 
H31.00005: Ionization potentials and static dipole polarizabilities of polyacenes using FermiLowdin selfinteraction corrected density functional approximation Sharmin Akter, Yoh Yamamoto, Luis Basurto, Tunna Baruah, Rajendra Zope We study the static electric dipole polarizabilities and the first ionization potentials of polyacenes from benzene to pentacene using the FermiLowdin Orbital based selfinteraction corrected (FLOSIC) density functional method. Most common density functional approximations (DFA) that often accurately predict equilibrium properties show deviation from the piecewise exact linear behavior between integer electron numbers. These functionals favor fractional charges and cause excessive electron delocalization resulting in incorrect electron densities. Due to delocalization errors, the ionization potentials obtained using the LDA and PBE functionals rapidly decrease as a function of length. The application of the FLOSIC method shows that it corrects for this manyelectron selfinteraction error in ionization potentials of polyacenes. Furthermore, it is observed that the FLOSIC corrected electron density when used in simple LDA functionals results in a remarkably accurate prediction of the ionization potentials of polyacenes. 
Tuesday, March 5, 2019 4:18PM  4:30PM 
H31.00006: Enhancing the efficiency of density functionals with a novel isoorbital indicator James Furness, Jianwei Sun The accuracy and efficiency of a density functional depends on the basic ingredients it uses and how the ingredients are built into the functional as a whole. An isoorbital indicator based on the electron density, its gradients, and the kinetic energy density, has proven an essential dimensionless variable allowing density functionals to recognise various types of chemical bonding, both strong and weak. Density functionals constructed around the isoorbital indicator usually require dense realspace grids for numerical implementation that deteriorate computational efficiency, compromising the improved accuracy. A novel isoorbital indicator is proposed based on the same ingredients that retains the capability to identify the same chemical bonds while relieving the requirement of dense grids. The novel isoorbital indicator improves recognition of electron density tail regions and is constraintfree for the exchangecorrelation potential. The novel isoorbital indicator is therefore expected to be the prime choice for density functional development and we discuss aspects of its use in cutting edge metageneralised gradient approximations. 
Tuesday, March 5, 2019 4:30PM  4:42PM 
H31.00007: WITHDRAWN ABSTRACT

Tuesday, March 5, 2019 4:42PM  4:54PM 
H31.00008: Gapping of MnO, FeO, CoO, and NiO Mott insulators by SCAN without U Yubo Zhang, Zhi Wang, Alex Zunger, Jianwei Sun Mott insulation is generally enabled by the physics of symmetry conserving onsite interelectronic repulsion U on single 3d sites via the celebrated Hubbard Model. DFT, exact for the ground state properties in principle, can not consistently open band gaps for MnO, FeO, CoO, and NiO Mott insulators if one uses symmetry conserving structures along with conventional semi local approximations to its exchange correlation functional. It has been recently shown [1] that using energylowering symmetry breaking mechanisms, DFT+U which distinguishes occupied and empty orbitals, opens band gaps for the monoxides. Here we show that even without invoking U, the semi local SCAN density functional [2] whose potentials are orbital dependent via the kinetic energy density dependence, opens band gaps for the monoxides in their AFM and PM (modeled with SQS) phases. The mechanism of gapping is analyzed. This success revives DFT for d electron materials and encourages the development of more sophisticated density functionals. 
Tuesday, March 5, 2019 4:54PM  5:06PM 
H31.00009: The JahnTeller effect in density functional theory Mark Palenik, Brett Igor Dunlap, Daniel Gunlycke Using degenerate perturbation theory, Jahn and Teller proved that openshell molecules with symmetry distort into lower symmetry configurations. Extending this proof to KohnSham (KS) density functional theory (DFT) is not straightforward because of the nonlinear Coulomb and exchangecorrelation potentials. These potentials affect the relationship between nuclear symmetry and electronic degeneracy, altering degenerate perturbation theory itself. Using our recently developed degenerate density functional perturbation theory, we define a perturbative approach to JahnTeller distortions for KS DFT. We use fractional occupation numbers to symmetrize the initial electron density, artificially stabilizing the nuclei in the highest possible symmetry. Using secondorder perturbation theory, we find the changes in geometry that occur when the symmetry of the electron density is broken to form a state with integer occupation numbers. This methodology allows us to retain many of the computational benefits of working in higher symmetry. We demonstrate the resulting equations in a system of ten electrons in a superatomlike harmonic oscillator potential. 
Tuesday, March 5, 2019 5:06PM  5:18PM 
H31.00010: Selfinteraction corrected dipole polarizabilites of free atoms and their ions Kushantha Pradeep Kumara Withanage, Sharmin Akter, Chandra Shahi, Tunna Baruah, Rajendra R Zope, John P Perdew, Juan Peralta, Koblar Jackson Conventional density functional theory (DFT) suffers from electron selfinteraction error (SIE) and hence tends to underbind the electrons. As a consequence, within DFT the electrons’ density in free atoms and their ions tends to be too responsive to an external electric field. Selfinteraction corrected density functional theory (SICDFT) calculations improve the description of electron binding, because the unphysical SIE is removed. We apply FermiLöwdin orbital selfinteraction correction (FLOSIC) to calculate static dipole polarizabilites of free neutral atoms, their cations and their anions. We compare FLOSICDFT polarizabilites of these systems against results from parent DFT functionals. We find FLOSICDFT polarizabilites agree better with experimental and accurate quantum chemistry calculation result 
Tuesday, March 5, 2019 5:18PM  5:30PM 
H31.00011: Performance of the FermiLowdin SelfInteraction Correction Method in Combination with metaGGA Functionals Yoh Yamamoto, Carlos Manuel Diaz, Rajendra Zope, Tunna Baruah Despite the success of DFT in describing the electronic properties of many electrons systems, the most widely used density functional approximations (DFA) suffer from selfinteraction errors which limit their predictive power. We have recently implemented the metaGGA functionals including the recent SCAN functional [1] that satisfies all 17 known exact constraints and is appropriately normed in the FermiLowdin SelfInteraction Correction (FLOSIC) code [2,3]. The FLOSIC is a sizeextensive implementation of the selfinteractionfree DFA. In this talk, we present the results of FLOSIC calculations using the metaGGA functionals. We present the performance of FLOSIC in combination with metaGGA functionals in total energies, ionization potential, and atomization energies of various atoms and molecules. 
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